High molar mass cyclic poly(-lactide) obtained by means of neat tin() 2-ethylhexanoate

l -Lactide was polymerized in bulk at 120, 140, 160 and 180 °C with neat tin( ii ) 2-ethylhexanoate (SnOct 2 ) as the catalyst. At 180 °C the Lac/Cat ratio was varied from 25/1 up to 8000/1 and at 160 °C from 25/1 up to 6000/1. The vast majority of the resulting polylactides consist of cycles in combination with a small fraction of linear chains having one octanoate and one COOH end group. The linear chains almost vanished at high Lac/Cat ratios, as evidenced by MALDI-TOF mass spectrometry and measurements of intrinsic viscosities and d n /d c values. At Lac/Cat ratios